The invention relates generally to an apparatus for electrically stunning animals to be slaughtered, in particular pigs. More specifically, the invention relates to apparatus comprising two endless conveyors which are operated parallel to each other and at a synchronized rate and are positioned to form a substantially V-shaped passageway between the operating surfaces thereof, and a pair of electrodes or sets of electrodes, which are insulated with respect to each other and are adapted to extend downwardly into said V-shaped passageway. Said electrodes are further adapted to engage the head of the animal to be stunned and to clear said passageway. Means is provided to substantially eliminate or reduce the difference in velocity of the electrodes relative to the conveyors upon closure of the current circuit between said electrodes or said sets of electrodes.
A similar apparatus has been described in co-pending application Ser. No. 147,827, now Pat. No. 4,338,700 which is based upon Dutch patent application 79.03681 not published in advance, which patent application constitutes a further development of the apparatus disclosed in application Ser. No. 905,371, which is based upon Dutch patent application 77.05519.
In the apparatus disclosed in the aforementioned applications, the electrodes or sets of electrodes are arranged in a spaced relationship to each other in line with the direction of conveyance. Consequently, the animal transported by the conveyors is first engaged by the first electrode or first set of electrodes which slides across the head of the animal, and only upon engagement with the second electrode or the second set of electrodes a current starts to flow. Initially, the current is of slight intensity for determining whether a proper contact has been made, and, upon detecting a proper contact, a jolt of current of sufficient intensity to cause the stunning is applied.
As has been explained already in application Ser. No. 147,827, based upon Dutch patent application 70.03681, when stunning one has to take care that no improper or insufficient current passage occurs during stunning, because such an improper or insufficient stunning current will tend to result in damaging or reducing the quality of the meat of the animal to be slaughtered. The current passage or flow required for the stunning should also pass directly through the head of the animal at the correct potential and correct intensity. When such current passage or flow is insufficient or improper, muscular contractions may occur in the animal causing bone breakage and internal bleeding. The meat of such an animal must then be classified as a lower quality grade or class.
Conventional manual stunning may be accomplished by using stunning rods which may be manually placed upon the animal and made to engage the head of the animal either in the longitudinal direction with respect to the animal's body or in a direction transverse thereto. When manual stunning is performed at a slow production rate, the percentage of animals that may not be considered to be of prime quality because of internal bleeding and bone breakage is relatively low and amounts to only a few animals per one thousand. Manual stunning presents, however, the drawback of limited production rates, because human operators are not capable of performing manual stunning above certain low production rates without seriously affecting efficiency. When attempting to increase production rates with manual stunning, the drop out percentage increases because the operators performing the manual stunning are subjected to great stress.
Furthermore, to avoid the situation where the animal to be stunned only loses motor neuron control and hence only seems to be stunned but has not been rendered unconscious it is desirable to use a higher voltage than would be safe for human operators.
Previously, my prior apparatus disclosed in application Ser. No. 905,371, caused a higher drop out percentage than that occurring from manual stunning, i.e., a greater percentage of lower quality grade meat was obtained from animals automatically stunned with my prior apparatus as opposed to those stunned with manual stunning techniques. As a consequence thereof, there has been an assiduous search for further improvements of automatic stunning apparatus, such as the provision of a dampening device for dampening the movements of the electrodes as disclosed in co-pending application Ser. No. 147,826, which is based upon Dutch patent application 79.03678; the maintenance of a fixed distance between the electrodes as disclosed in co-pending application Ser. No. 147,826, which is based upon Dutch patent application 79.03680; and the joint or simultaneous movement of the electrodes and the animal as disclosed in co-pending application Ser. No. 147,826, which is based upon Dutch patent application 79.03681. Although these improvements aid in decreasing the drop out percentage caused by improper automatic stunning, the apparatus of the present invention provides even more efficiency.
A feature of the present invention is to provide an apparatus in which the occurrence of dropout will be lower than that in manual stunning.